The invention relates to a belt retractor for a vehicle seat belt rising a frame provided with plural locking teeth, a belt reel rotatably supported in the frame and a locking tooth system corresponding to the locking teeth and comprising a locking mechanism with is adapted to transfer the belt reel from a home position in which it is freely rotatable into a locking position in which the locking tooth system of the belt reel engages in the locking teeth of the frame, wherein at least one pivoting control lever is provided in which one side of the belt reel is rotatably supported and which is adapted to guide the belt real from the home position into the locking position.
A belt retractor of this type makes use of a displacement of the belt reel (more exactly speaking at least one side of the belt reel) for locking the belt red. The displacement results in the locking tooth system of the belt reel being guided into the locking teeth of the frame. This prevents the belt reel from rotating in the take-off direction of the belt webbing. The rotation against a high resistance moment which is nevertheless possible due to a possibly provided force limiter is left aside in this context.
The locking mechanism is in charge of ensuring that the locking tooth system engages in the locking teeth in the correct position. The locking mechanism causes pre-locking of the belt reel in the control lever at predetermined angular positions of the locking tooth system which is adjusted to the position of the locking teeth. The way in which the locking mechanism brings about said pre-locking (i.e. prevention of rotation relative to the control lever) is known per se. What is important is that the pre-locking requires rotation of the belt reel in the unwinding direction, until the belt reel is pre-locked either due to a vehicle-sensitive blocking or a webbing-sensitive blocking. When in the pre-locked state a tensile force is exerted on the webbing, said tensile force causes the belt reel guided by the control lever to be pulled toward the locking teeth and to finally engage in the latter.
It is a drawback of such belt retractor that the control lever can guide the belt reel to the locking teeth even if the belt reel is not pre-locked and no tensile force acts on the webbing, either. This can happen especially when high acceleration (or deceleration) acts on the belt retractor, thus resulting in displacement of the control lever together with the belt reel. Any deceleration required for this purpose, however, is so high due to a usually provided reset spring that in most cases it is only reached in the case of crash. Therefore, it would basically be considered to be positive to have the belt reel engage in the locking teeth already at an early point in time. However, this type of engagement of the locking tooth system in the kicking teeth does not ensure that a positional correct engagement is brought about. It cannot be excluded that tooth crests abut on tooth crests, which in the case of a subsequent load might result in the fact that the locking tooth system does not engage in the locking teeth at all.